Hillary Clinton managed to draw out a 0.5% margin over rival Bernie Sanders in the hard-fought Kentucky Democratic primary, while Sanders took and held an early lead in Oregon, handing him a boost in the primary home stretch.

Donald Trump sailed to an easy victory in the sole Republican primary in Oregon, since both of his rivals on the ballot — Ted Cruz and Jon Kasich — had already dropped out of the race. With 61% of the precincts reporting, Trump had 66.8% of the vote to Kasich's 16.9% and Cruz's 16.3%.

Sanders and his supporters were flying high on the Oregon win. With 64% of the tally in, Sanders grabbed 53.4% to Clinton's 46.6%.

"We are going to win Washington, we just won Oregon, and we are going to win California. I am getting to like the West coast," he said to the roar of thousands of supporters in an arena in Carson, California, where the mighty primary race in that delegate-rich state will be fought in June.

The tone was far more subdued in Clinton country. With 99% of the votes tallied in the Kentucky race, Clinton led Sanders just 46.8% to 46.3% by a margin of 1,923 votes. CNN declared Clinton the winner, but the race was such a call that the Associated Press (AP) did not.

Kentucky Secretary of State Allison Lundergan Grimes – a Clinton supporter – announced Clinton as the "unofficial" winner of the primary race.

Grimes, who has campaigned with Clinton, said that 769 votes were untabulated and as Clinton led with 1,923 votes, the numbers were on her side. "Hillary Clinton will be the unofficial nominee on behalf of the Democratic party here in the commonwealth of Kentucky," Grimes declared.

The unofficial announcement was enough for Clinton, who declared victory in the Bluegrass State and thanked voters for their support. "We just won Kentucky! Thanks to everyone who turned out. We're always stronger united," Clinton tweeted.

Although Clinton was eager to declare a win in Kentucky, the slim margin against Sanders does not bode well for her.

Sanders' campaign manager Jeff Weaver told CNN that the tight race in Kentucky was a sign that Democratic voters "are having second thoughts" about Clinton. "The media is ready to call this race over, but I think voters in the various states want to see this race go on." Sanders has maintained the race is far from over, but a look at delegate counts tells another story.

Clinton leads with 2,265 delegates to Sanders' 1,498 when superdelegates are included. Democratic candidates need 2,383 delegates to clinch the nomination. The two split Kentucky's 55 delegates, with each receiving 25 delegates. Sanders' win in Oregon nets him an estimated 28 delegates to an expected 24 for Clinton, but those numbers will do very little to close the 767 delegate gap between the two candidates.

Looking ahead to 7 June primaries and the July convention

The Vermont senator is pinning his hopes on California, which holds its primary on 7 June and has 475 delegates at stake. He has been vigorously campaigning in the Golden State, but recent polls show Clinton is clearly favoured.

A KABC/SurveyUSA poll, conducted from late April, placed Clinton ahead by 19 points, a total of 57 to 38. Three other polls in April also show her ahead by as little as two points (Fox News) and as much as 12 points (CBS News/YouGov). Five other states will also hold primaries on 7 June.

According to The Guardian, Sanders will need to win 67% of the remaining pledged delegates to win a majority and claim the party nomination. Sanders, in a speech made in California after his loss in Kentucky, was confident he could do it. "We have the possibility. It will be a steep climb, I recognise that. But we have the possibility of going to Philadelphia with the majority of the pledged delegates."